At extremely cold temperatures, the quantum nature of matter expresses itself in unique collective behaviors. These include superconductivity, superfluidity, and Bose-Einstein condensation, where collections of particles act as a single quantum system. Most of these dramatic effects have been achieved with collections of atoms. Molecules could potentially display even more interesting behaviors, since they have fundamental asymmetries and long-range interactions among their atoms.

Up until now, these same properties have made it difficult to bring molecules down to the same temperatures as individual atoms. But a new experiment cooled populations of roughly a million fluoromethane molecules to a fraction of a degree above absolute zero. Martin Zeppenfeld and colleagues used a combination of three different forms of light to extract energy from the molecules inside an electrical trap, a trick known as Sisyphus cooling. The assembly maintained this ultracold state for up to 27 seconds, long enough to reveal unique quantum phenomena—including possibly Bose-Einstein condensation of molecules.

Individual atoms are fairly symmetrical in terms of their electric charge distribution, at least under ordinary conditions. This means their interactions are fairly short-ranged: two atoms must be brought relatively close before the internal distribution of electrons and protons can influence each other. On the other hand, molecules—most notably water—may be strongly polar, with a significant accumulation of negative charge on one side of the molecule balanced by positive charge on the other. This occurs even though the molecule as a whole is still electrically neutral.

Polar character is significant for a number of reasons, most notably because polar molecules tend to sit in particular orientations relative to each other. The accumulation of charge also means interactions between molecules stretch farther in space than they do for neutral atoms, with the interaction strength and direction varying depending on how the molecules are aligned. The chirality or "twist" of a molecule can also have a significant influence, especially in complex biological molecules.

All of these properties could have consequences at the quantum level. However, the widely used methods for cooling and trapping neutral atoms don't work with polar molecules. This failure is, ironically, partly for the same reasons we'd want to chill them in the first place: their asymmetries and their electrical interactions get in the way.

Bombarding the molecules with photons to slow them down, which works with atoms, won't help, because the interactions among molecules are stronger than their interactions with the light. Cooling molecules requires stronger stuff, something that can achieve faster extraction of energy.

For this reason, the researchers in the present study turned to a more elaborate technique, where multiple processes were utilized in succession to cool the molecules. The experimenters sent a stream of molecules into a trap made from standing microwaves crossed with an infrared laser beam. The trap itself consisted of a sort of radio antenna; by varying the frequency of the radio waves, the researchers could extract energy from the molecules rapidly.

The combination of the excitation with a laser and the jostling by radio waves boosted the energy state of the molecules slightly, but they lost even more energy when coming down, resulting in ever colder temperatures. This virtual harassment to produce ultracold temperatures gives the process its name of Sisyphus cooling, referring to the Greek myth of a wicked king punished in Hades to repeat a single task forever.

The researchers used fluoromethane (CH3F), a polar molecule in which fluorene substitutes for one hydrogen atom in methane (CH4). They managed to cool and contain the molecules for up to 27 seconds—while that's short on the human scale, is sufficiently long on the quantum scale to perform experiments. Fluoromethane (and I repeat it because it's a fun word) is also a stand-in for many other molecules that could be used, including some that are chemically important, or that have interesting physical properties like chirality.

Many collective phenomena in cold quantum systems mimic those in high energy physics; see these articles on Majorana fermions and Higgs-like behavior in nanomaterials for two recent examples. Polar and chiral molecules could exhibit exotic collective behaviors at cold temperatures, such as parity violation, where processes depend on which direction in space the particles are moving. Additionally, a Bose-Einstein condensate involving polar molecules would open up an entirely new regime for studying these systems. The current experiment was only the beginning; future tests could lead to some exciting new results.

I predict that this method of harassing molecules to achieve colder temperatures will accidentally result in achieving a temperature below absolute zero. This violation of a cosmic threshold will trip the circuit breaker on the universe and we'll all suddenly wink out of existence.

I predict that this method of harassing molecules to achieve colder temperatures will accidentally result in achieving a temperature below absolute zero. This violation of a cosmic threshold will trip the circuit breaker on the universe and we'll all suddenly wink out of existence.

As ludicrous as it sounds, we have observed temperatures "below absolute zero." We didn't wink out of existence, but it may have been responsible for the 1970s.

Knowing that water is polar in while being neutral and that the molecules tend to orient a particular way makes my programmer head spin. Just a bit, now when I see a glass of water I can imagine all the little molecules lining up, getting ready to be ice. Or Ice 9.

The experimenters sent a stream of molecules into a trap made from standing microwaves crossed with an infrared laser beam. The trap itself consisted of a sort of radio antenna; by varying the frequency of the radio waves, the researchers could extract energy from the molecules rapidly.

You are saying we can make a rapid anti-microwave oven to turn food cold rapidly? That'd be awesome. Ice lollies takes too long to make at the moment

The experimenters sent a stream of molecules into a trap made from standing microwaves crossed with an infrared laser beam. The trap itself consisted of a sort of radio antenna; by varying the frequency of the radio waves, the researchers could extract energy from the molecules rapidly.

I found this very interesting; for years now I've been fantasizing about a microwave-like device that could cool things down in seconds (think about popping in a beer and having a cold one in like 30 secs), only to be told that it wasn't possible, at least not with microwave technology. Has anyone got an idea about how they did it and if it could be applied to the appliance market?